The present invention relates to novel silanes and silicic acid polycondensates and partial polycondensates formed from them in which there is an organic radical bonded to a silicon atom, said radical being branched and carrying at least one independently organically polymerizable group on each of the two branches or comprising one such a group on one of the two branches and a radical with an additional silicon atom on the other. The second of these two groups, or the silicon atom-containing radical, is bonded via an acid amide, urethane, or carboxylic acid ester group to said organic radical. The invention furthermore comprises various processes for the production of these condensates as well as polymerizates and composites produced therewith.
Silicic acid heteropolycondensates, obtainable by hydrolysis and condensation of silanes with hydrolyzable groups, have been known for a long time (see, for example DE PS 27 58 414). Such condensates can be processed to form many products, for example, to form coverings, coatings, membranes, or bulk materials. The underlying silanes can also comprise double bonds or other organically reactive groups through which they can be polymerized into an organic network (see, for example DE 40 11 044 C2 and DE 44 05 261 A1). A quite specific group of such materials can be obtained from silicic acid polycondensates which comprise a radical bonded to the silicon atom, said radical comprising, in addition to at least one organically reactive group, a free hydroxy or carboxylic acid group. Such silicic acid polycondensates are described in DE 44 16 857 C1. They are suitable, alone, in mixtures, or together with other hydrolyzable, condensable, or polymerizable components, for the production of scratch-resistant coatings, filling materials, adhesive materials, sealing materials, shaped bodies, or embedded materials. The group of compounds described in DE 44 16 857 C1 is furthermore distinguished by the fact that the distance between the silicon atom and reactive or double bond(s) can be set arbitrarily, on account of which the physical characteristics of the condensates or polymerizates thus obtained can be set over wide ranges.
The carboxylic acid group of the carboxylic acid-modified silanes of DE 44 16 857 C1 are charge carriers and thus make possible, for example, the production of dispersions, emulsions, or electropaints. Furthermore, these groups can be complexed with suitable metal compounds of titanium, zirconium, tin, and others, or, in the case of free hydroxy groups, even function as a complexing agents, which can have a positive effect on the X-ray opacity, contact toxicity, and the increase of the index of refraction. The combination of carboxyl groups with polymerizable C═C double bonds in connection with the inorganic silane portion represents an ideal compound for use as polyalkene acids in ionomer cements. However, in many cases one needs systems with a lower hydrophilicity of the matrix than that of the condensates which are obtained from the compounds from DE 44 16 857 C1 since for systems with a lower hydrophilicity of the matrix their water uptake in the presence of moisture would be reduced, their wet strength increased, and the viscosity of the resins lowered. Moreover, a still higher organic cross-linking potential and thus a general increase of the strength is desirable.
It is the objective of the present invention to provide such systems as well as the silanes needed for them and in fact via the insertion of a specific grouping into them which in other respects makes possible a great variability of the other structural elements and thus of the properties of the resins and polymerizates which can be produced.